Image reading apparatus and image data processing method

ABSTRACT

Correction of brightness of image data outputted by an image sensor which includes a light emitting portion, a photoelectric conversion portion in which a plurality of photoelectric transducers are arrayed in line, and a charge transfer portion. For a smear occurred at the charge transfer portion, reference smear amount data is stored, corresponding to each of color components of light from the light emitting portion and a correction target pixel. A correction amount for brightness is based on a difference between brightness values of a first color component and a second color component and the reference smear amount data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image reading apparatus and imagedata processing method. Particularly, the present invention relates toan image reading apparatus and image data processing method forcorrecting an abnormal image caused by a smear when reading an image byoptically scanning the image original.

2. Description of the Related Art

Some conventional image reading apparatuses use a contact image sensor(to be simply referred to as a CIS) as an image sensor for scanning anoriginal. An apparatus of this type sequentially switches and uses threeLEDs for emitting light beams of R, G, and B color components toirradiate the original surface with light. Thus, image data are read outline-sequentially in order of the color components of one line.

FIG. 8 is a timing chart showing LED turn-on and readout in imagereading.

As shown in FIG. 8, one line (cycle of a signal L_(sync)) is dividedinto three periods (cycle of a signal H_(sync)). LEDs are turned on inorder of a red LED LED_R, green LED LED_G, and blue LED LED_B, storingcharges. The stored charges are transferred outside the LED during theperiod of the signal H_(sync) in the next cycle. For example, duringperiod “A”, exposure and charge storage by the red LED are performed. Atthe same time, charges obtained by exposure and charge storage by theblue LED for a preceding line are transferred outside.

FIG. 9 is a view showing the schematic arrangement of the image sensor.

The LED irradiates an image original with light. When the lightreflected by the image original enters the array of a photodiode 201,charges are stored to generate an image signal. The signal chargesstored in the array of the photodiode 201 are sent to a verticaltransfer register 202, and held for a period until they are horizontallytransferred. At the transfer timing, the signal charges are sent to ahorizontal transfer register 203. The signal charges are thentransferred to an output circuit (not shown) via the horizontal transferregister 203.

In this arrangement, portions except for the photodiode 201 are shieldedfrom light by an aluminum light shield (not shown) to prevent generationof unwanted charges. However, the light shielding is sometimesinsufficient due to layout restrictions of the apparatus and device, orthe like. For example, when an aluminum wire for transferring anelectrical signal is used even for light shielding and a wire differentin potential is arranged, this wire cannot be connected to the signalline. An aluminum wire slit is generated between non-equipotentialportions, degrading the light shielding ability compared to theremaining portion. In this case, unwanted light enters from the slit,generating unwanted charges. The unwanted charges are added to a normalsignal, outputting a signal higher in strength than the normal signal(signal indicating a brighter state). This phenomenon is called a smear.

A fundamental countermeasure against the smear is to prevent incidenceof unwanted light. For example, if a smear occurs due to unwanted lightentering a charge transfer portion such as a vertical transfer registeror horizontal transfer register, enhancing a light shield above thecharge transfer portion so as to prevent incidence of unwanted light canbe a fundamental countermeasure. However, the wafer area of the circuitboard in recent apparatuses is decreasing for cost reduction, and itbecomes difficult to achieve a good aluminum light shielding effect. Onthe other hand, the degree of aluminum light shielding effect depends onthe manufacturing precision of the aluminum light shielding plate, andless varies. This is the structural issue of the aluminum lightshielding plate, so a smear occurs at the same location if the incidentlight quantity is the same.

Conventionally, countermeasures to correct degradation of the imagequality caused by the smear have been proposed. For example, in JapanesePatent Laid-Open No. 2007-201553, after charges generated by a pluralityof light reception elements effective for image capturing aretransferred to a charge transfer portion, correction data is generatedbased on data obtained from an output signal in an additional transferoperation executed in addition to a transfer operation for the chargesreceived by the charge transfer portion.

However, the conventional technique requires an additional chargetransfer operation, prolonging the time taken for image reading. In theconventional technique, since no smear occurrence position is known inadvance, it is necessary to locate where the smear occurs. If thedetection fails, correction processing becomes less effective. Furtherin the conventional technique, the amount of exposure by the lightemitting element is not always constant. The occurrence amount of everysmear varies, impairing the correction effect.

The degree of influence of output level variations caused by the smearchanges depending on the irradiation light quantity of the LED. Thus,uniformly subtracting the light quantity does not lead to correction.For example, in a line-sequential reading method of reading out signalsby sequentially switching and turning on red, green, and blue LEDs, thebrightness levels of the R, G, and B color components change dependingon the color balance of an original. The brightness level is a reflectedlight quantity level obtained from reflected light of light whichirradiates an original. When the reflected light quantity level changes,the smear amount also changes, and uniform correction does not work.

In the first place, the smear occurs when charge transfer and exposureare executed simultaneously. Occurrence of the smear can, therefore, beprevented by performing exposure and charge transfer in differentperiods. However, performing exposure and charge transfer in differentperiods results in prolonging the image reading time and decreases theperformance.

The time necessary for charge transfer may be shortened by quicklyexecuting charge transfer. If the time necessary for charge transfer canbe shortened, exposure is performed in the remaining time, enablingexecution of charge transfer and exposure in different periods. However,implementation of fast charge transfer requires a high-speed clock,increasing unwanted radiation and noise.

Charge transfer and exposure may be performed in different periods byincreasing the irradiation light quantity from the light source toshorten the exposure time. However, introduction of a high-output lightsource has problems such as high apparatus cost and light quantityvariations under the influence of heat generated by the high-outputlight source.

SUMMARY OF THE INVENTION

Accordingly, the present invention is conceived as a response to theabove-described disadvantages of the conventional art.

For example, an image reading apparatus and image data processing methodaccording to this invention are capable of effectively correcting asmear without increasing the cost and degrading the performance.

According to one aspect of the present invention, there is provided animage reading apparatus comprising: an image sensor including a lightemitting portion, a photoelectric conversion portion in which aplurality of photoelectric transducers are arrayed in line, and a chargetransfer portion which transfers charges stored in the photoelectricconversion portion; a first memory which stores, for a smear occurred atthe charge transfer portion, reference smear amount data correspondingto each of color components of light from the light emitting portion andeach of the photoelectric transducers; an image processing unitconfigured to, for image data inputted by the image sensor, obtain acorrection amount for a brightness value based on a difference betweenbrightness values of a first color component and a second colorcomponent and the reference smear amount data stored in the firstmemory, and correct a brightness value of the image data inputted by theimage sensor based on the correction amount.

According to another aspect of the present invention, there is provideda method for processing image data inputted by an image sensor includinga light emitting portion, a photoelectric conversion portion in which aplurality of photoelectric transducers are arrayed in line, and a chargetransfer portion which transfers charges stored in the photoelectricconversion portion, comprising: for the image data inputted by the imagesensor, obtaining a difference between brightness values of a firstcolor component and a second color component; for a smear occurred atthe charge transfer portion, obtaining a reference smear amount datacorresponding to each of color components of light from the lightemitting portion and each of the photoelectric transducers; obtaining acorrection amount for a brightness value from the difference between thebrightness values and the reference smear amount data; and correcting abrightness value of the image data inputted by the image sensor based onthe correction amount.

The invention is particularly advantageous since the influence of smearcan be reduced without increasing the apparatus cost and degrading thereading performance even when reading an image using an image sensorwhere occurrence of a smear is unavoidable.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view showing the schematic arrangement of animage reading apparatus as an exemplary embodiment of the presentinvention.

FIG. 2 is a side sectional view showing the detailed structure of acontact image sensor (CIS) unit.

FIG. 3 is a block diagram showing the arrangement of the control circuitof the image reading apparatus.

FIG. 4 is a diagram showing an outline of smear correction.

FIG. 5 is a schematic view showing the correction target pixel.

FIG. 6 is a graph showing the correlation between the density differenceand the correction amount.

FIG. 7 is a flowchart showing an outline of smear correction processing.

FIG. 8 is a timing chart showing typical timings in line-sequentialreading.

FIG. 9 is a schematic view showing the schematic arrangement of an imagesensor.

DESCRIPTION OF THE EMBODIMENTS

An exemplary embodiment of the present invention will now be describedin detail in accordance with the accompanying drawings. It should benoted that the relative arrangement of building components and the likeset forth in the embodiment do not limit the scope of the presentinvention unless it is specifically stated otherwise.

FIG. 1 is a side sectional view showing the arrangement of an imagereading apparatus (scanner) which reads a reflection original using aCIS as an exemplary embodiment of the present invention.

As shown in FIG. 1, an image original (not shown) is set on a platenglass 20, and an original pressure plate 30 prevents the float of theimage original from the platen glass 20. The original pressure plate 30also functions as a contamination/damage prevention cover for the platenglass 20.

When a light source 40 including an LED lamp and light guide irradiatesthe image original, a contact image sensor (CIS) 60 reads lightreflected by the image original via a lens array 50 withoutenlargement/reduction. A contact image sensor (CIS) unit 300 is formedfrom the light source 40 and CIS sensor 60, and arranged in tightcontact with the platen glass 20.

In this apparatus, while a motor 70 moves the CIS unit 300 in adirection (sub-scanning direction) indicated by an arrow B, the CIS unit300 is electrically scanned in a direction (main scanning direction)perpendicular to the drawing sheet surface to read the image original.In general, the motor 70 is a stepping motor, DC motor, or the like. Inimage reading, a white reference board 10 is irradiated with light,obtaining a reference signal for performing shading correction. Thewhite reference board 10 is generally made of a material with which thetint hardly varies regardless of environmental conditions such astemperature and humidity, and durability.

In this arrangement, when reading an image original, shading correctionusing the white reference board 10 is executed in advance. At the sametime, the dimming operation of the LED light source is performed to keepthe exposure amount constant.

FIG. 2 is a side sectional view showing the detailed structure of theCIS unit 300.

As shown in FIG. 2, the CIS unit 300 includes, in correspondence withthe three primary colors of light, a red LED 303 which emits red light,a green LED 304 which emits green light, and a blue LED 305 which emitsblue light. In original reading, the respective color LEDs are turned ontime-divisionally for each line. The original is uniformly irradiatedwith the emitted light through a light guide 302, and a SELFOC Lens® 301condenses the reflected light for each pixel. The light is formed intoan image on a photoelectric transducer (not shown: light receptionelement) in the CIS unit, and the received light is converted into anelectrical signal. In this way, an image signal of one line includingthe color signals of the R, G, and B color components is output. Bymoving the CIS unit 300 in the sub-scanning direction, an image on theentire original surface is read. Note that the direction of the arrow Aindicating the array direction of the cells of the SELFOC Lens® 301 willbe called the main scanning direction. The main scanning direction andsub-scanning direction are perpendicular to each other.

In FIG. 1, the main scanning direction is perpendicular to the drawingsheet surface.

As is apparent from this structure of the CIS unit, a plurality of lightreception elements are arrayed in line in the CIS unit 300 to form alight reception portion. Hence, a smear potentially readily occursstructurally at the charge transfer portion from the light receptionportion of the CIS unit.

FIG. 3 is a block diagram showing the arrangement of the control circuitof the image reading apparatus.

The CIS unit 300 line-sequentially reads a color image by switching andturning on the respective color LEDs 303 to 305 for each line by an LEDdriving circuit 403. The LEDs 303 to 305 are light sources capable ofchanging the quantity of irradiation light to an original. The LEDdriving circuit 403 can arbitrarily turn on the LEDs 303 to 305.

In other words, it is possible to sequentially turn on the LEDs 303 to305 one by one, two of them, or according to circumstances, all thethree. An amplifier (AMP) 404 amplifies a signal output from the CISunit 300. An A/D conversion circuit 405 A/D-converts the amplifiedelectrical signal, outputting, for example, digital image data of 16bits for each color component of each pixel. An image processing unit600 processes the digital image data converted by the A/D conversioncircuit 405. An interface 406 receives image data from the imageprocessing unit 600, exchanges control data with an external apparatus412, and outputs image data. The external apparatus 412 is, for example,a personal computer (not shown). The personal computer issues aninstruction such as image reading (scanning) to a CPU 409 via theinterface 406.

Note that the image reading apparatus shown in FIG. 1 is asingle-function (scanner function) apparatus which is connected to theexternal apparatus 412 and operates. However, the image readingapparatus may be configured as a multi-function printer by integratingit with an image printing unit 700. In this case, image data from theimage processing unit 600 can be output to the image printing unit 700.

The image data from the interface 406 is converted into binary dataindicating “print” or “not print” for each pixel. An image is printed ona printing medium using a printing material. The image printing unit 700can be an inkjet printer, a laser beam printer using anelectrophotographic method, a sublimation printer, or the like. Theseprinters are well known and a detailed description thereof will beomitted.

The CPU 409 in the form of a microcomputer controls an operationinstruction from an operation unit 4. This control is executed byreading out a processing program stored in a ROM 410 by the CPU 409, andexecuting it using a RAM 411 as a work area. In FIG. 3, a referencesignal oscillator (OSC) 407 is, for example, a crystal oscillator. Atiming signal generation circuit 408 divides the frequency of an outputfrom the reference signal oscillator 407 in accordance with the settingsof the CPU 409, generating various timing signals each serving as thebase of an operation.

An LED 414 serves as the backlight of an LCD 110. Lighting of the LED414 is controlled by a lighting signal output from the timing signalgeneration circuit 408.

This embodiment will exemplify correction when the line-sequentialreading method is adopted, and irradiation light from the red LEDaffects transfer of charges obtained by irradiation of the blue LED.Note that an arrangement in which charges are stored by reflected lightof irradiation light from the red LED and the stored charges aretransferred is called an R channel. Similarly, an arrangement in whichcharges are stored by reflected light of irradiation light from thegreen LED and the stored charges are transferred is called a G channel.An arrangement in which charges are stored by reflected light ofirradiation light from the blue LED and the stored charges aretransferred is called a B channel.

First, a method of measuring a smear reference amount will be explained.The influence of smear on the reading result increases in proportion tothe difference between the brightness values of the respective colorcomponents when a color image original is read. For example, if the Rcomponent brightness value=the B component brightness value, the readingresult is free from the influence of smear.

However, if the R component brightness value>>the B component brightnessvalue, the influence of smear becomes serious. In this case, it isestimated that the received light quantity of the B channel is verysmall and that of the R channel is large. The received light quantity ofthe R channel gives the influence of smear to the B channel, and thisresult serves as a reading result, affecting read image data. In thismanner, the relationship between the R component brightness value leveland the B component brightness value level, and the degree of influenceof smear on the reading result are measured and set as brightness levelconditions and a smear reference amount. For example, provided that eachpixel of the R, G, or B color component is represented by 8 bits, thebrightness value level of each pixel of the R, G, or B color componentvaries from 0 to 255. Assume that image data is obtained as a result ofreading an image original having an R component brightness valuelevel=200 and a B component brightness value level=20. In this imagedata, brightness abnormality occurs due to a smear at the position of apixel affected by the smear. For example, the B component brightnessvalue level is 20. However, if the brightness value of the pixelaffected by the smear is 25, correction for the brightness value isneeded for obtaining a correct brightness value. This corrected iscalled smear correction.

Next, a dimming operation will be explained. The image reading apparatusaccording to the embodiment performs a light source dimming operationbefore the start of image reading. Since the LED has large individualvariations, it is difficult to accurately estimate the smear amount.Thus, the white reference board whose brightness value level is known inadvance is read, the lighting period is changed to adjust the outputlevel to a target value so that the quantity of light emitted by the LEDis kept constant. By standardizing the light emission quantity, thesmear occurrence amount can be estimated.

FIG. 4 is a diagram showing an outline of smear correction. In theembodiment, the image processing unit 600 executes the smear correction.The ROM (first memory) of the image processing unit 600 or the likestores predetermined reference smear amount data (S(B)_(ref)) 103. Thereference smear amount data 103 is a value unique to each correctiontarget pixel. For each color component, data of each pixel in the mainscanning direction is stored.

The image processing unit 600 includes two memories 101 and 102 whichhold, for each line, data of the R, G, and B color components of twoconsecutive lines. These memories are also called the second memory withrespect to the ROM (first memory) which stores reference smear amountdata. The image processing unit 600 further includes a correctioncalculation unit 105 which calculates a correction amount based on thereference smear amount data 103, current line data and next line data,and a subtracter 104 which subtracts the correction amount S(B) from thecorrection target pixel. The correction amount is calculated inaccordance with equation (1). Note that the subtractor 104 includes abuffer for holding line data. Using the line data held by the buffer,the subtractor 104 performs subtraction for pixels of each line.

That is,S(B)=S(B)_(ref)·{(R ₁ −B ₁)/(R _(1ref) −B _(1ref))}  (1)where S(B) is the correction amount of the B channel, R₁ is the Rchannel brightness value level before correction, B₁ is the B channelbrightness value level before correction, S(B)_(ref) is the referencelevel (constant) of a smear amount occurred in the B channel, R_(1ref)is the R channel brightness value level (constant) when the referencelevel is obtained, and B_(1ref) is the B channel brightness value level(constant) when the reference level is obtained. In other words,equation (1) multiplies a coefficient and a difference betweenbrightness values of two color components. For example, provided thatS(B)_(ref)=5, R_(1ref)=220, and B_(1ref)=40, the coefficientvalue=5/(220−40)=1/36.

FIG. 5 is a schematic view showing the correction target pixel.

This embodiment employs the line-sequential reading method. Thus, thecorrection amount is calculated from a brightness value level at thesame pixel position in the main scanning direction while the colorcomponents adjacent in the sub-scanning direction are different. In theexample of FIG. 5, letting R(N,L), G(N,L), and B(N,L) be data of the R,G, and B color components in N pixel on L line, the correction amountfor B(N,L) is calculated based on the brightness value level of R(N,L+1)and the brightness value level of B(N,L). The image processing unit 600corrects B(N,L) based on the correction amount for B(N,L). Similarprocessing is made for the next (L+1) line. More specifically, the imageprocessing unit 600 calculates the correction amount for B(N,L+1) basedon the brightness value level of R(N,L+2) and the brightness value levelof B(N,L+1). Then, the image processing unit 600 corrects B(N,L+1) basedon the correction amount for B(N,L+1).

When the image processing unit 600 described with reference to FIG. 4 isused, the memory 101 stores image data of L line, and the memory 102stores that of (L+1) line. The correction amount is calculated accordingto equation (1) using image data of the R channel on (L+1) line, imagedata of the B channel on L line, and the reference smear amount. In acase where the next line is to be processed, the image processing unit600 performs control to store image data of (L+2) line into the memory101.

FIG. 6 is a graph showing the correlation between the density differenceand the correction amount. The reference amount serving as the base ofthe smear correction amount is measured under a given condition. Asshown in FIG. 6, a straight line connecting a density difference at thattime and the origin is the relation between the correction amount andthe density difference.

FIG. 7 is a flowchart showing an outline of smear correction processing.

First in an image reading apparatus in which smear correction isimplemented, a pixel where a smear occurs is located, and the locatedpixel is set as a pixel address in step S701. In step S702, a referencesmear amount corresponding to the pixel address set in step S701 is set.The reference smear amount has been calculated based on a smear amountmeasured in advance for each pixel.

In step S703, reading of an image original starts. Then, in step S704,the memories 101 and 102 functioning as line buffers store image data oftwo lines. In step S705, it is determined whether or not the processingline has reached the final line. If the processing line has not reachedthe final line, the process advances to step S706 to start searching fora correction target pixel. To the contrary, if the processing line hasreached the final line, the process ends. In this case, the line is animage reading line in the sub-scanning direction.

In step S707, pixels are checked in order in the main scanningdirection. In step S708, it is confirmed whether or not the searchtarget pixel has reached the final pixel in the main scanning directionon the processing target line. If the search target pixel has reachedthe final pixel, the process advances to step S704. If the search targetpixel has not reached the final pixel yet, the process advances to stepS709 to check whether or not the search target pixel is the correctiontarget pixel. If the search target pixel is the correction target pixel,the process advances to step S710 to perform the correction describedwith reference to FIGS. 4 and 5. If the search target pixel is not thecorrection target pixel, the process advances to step S707 withoutperforming the correction.

According to the above-described embodiment, while charges are storedupon irradiation of an LED of a given color, the correction amount isobtained using a reference smear amount which has been measured inadvance and stored. The brightness value level can be corrected usingthe correction amount. Even when charge storage for a given colorcomponent and charge transfer for another color component aresimultaneously performed for image reading according to theline-sequential reading method, the smear can be corrected, implementingmore accurate image reading. In the above-described embodiment, thecorrection coefficient for B(N,L) is calculated based on the brightnessvalue level of R(N,L+1). However, the correction amount for B(N,L) maybe calculated further based on the brightness value level of R(N+1,L+1)and that of R(N−1,L+1). More specifically, and the image processing unit600 calculates the correction amount for R(N,L) based on the brightnessvalue level of R(N,L) and the brightness value level of G(N,L). Theimage processing unit 600 corrects R(N,L) based on the correction amountfor R(N,L). Similarly, the image processing unit 600 calculates thecorrection amount for G(N,L) based on the brightness value level ofG(N,L) and the brightness value level of B (N,L). Then, the imageprocessing unit 600 corrects G(N,L) based on the correction amount forG(N,L).

The embodiment is also advantageous since the apparatus is capable ofcorrecting a smear at low cost because an arrangement using a specialelement or device is unnecessary. In addition, charge storage for agiven color component and charge transfer for another color componentcan be executed simultaneously, so the reading speed can be kept high.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-135511, filed Jun. 14, 2010, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image reading apparatus comprising: an imagesensor including a light emitting portion, a photoelectric conversionportion in which a plurality of photoelectric transducers are arrayed inline, and a charge transfer portion which transfers charges stored inthe photoelectric conversion portion, configured to output image datacorresponding to a plurality of pixels; a first memory which stores, fora smear occurred at the charge transfer portion, reference smear amountdata corresponding to each of color components of light from the lightemitting portion and a correction target pixel; an image processing unitconfigured to, for image data outputted by the image sensor, obtain acorrection amount for a brightness value based on a difference betweenbrightness values of a first color component and a second colorcomponent and the reference smear amount data stored in the firstmemory, and correct a brightness value of the image data outputted bythe image sensor based on the correction amount.
 2. The apparatusaccording to claim 1, further comprising a conversion unit configured toA/D-convert the charge transferred from the charge transfer portion. 3.The apparatus according to claim 1, further comprising a moving unitconfigured to move the image sensor in a direction diagonal to an arraydirection of the plurality of photoelectric transducers.
 4. Theapparatus according to claim 1, further comprising a second memory whichstores image data of at least two lines outputted by the image sensor.5. The apparatus according to claim 1, wherein the light emittingportion irradiates an original with light, and the photoelectricconversion portion receives the light reflected by the original.
 6. Theapparatus according to claim 1, wherein the reference smear amount datais obtained in advance by measurement.
 7. The apparatus according toclaim 1, further comprising a holding unit configured to hold lightemission quantities of three light sources included in the lightemitting portion constant.
 8. The apparatus according to claim 1,wherein the obtained correction amount is changed based on lightingperiods of three light sources included in the light emitting portion.9. The apparatus according to claim 1, wherein the light emittingportion includes a first light emitting device, a second light emittingdevice, and a driver for time-divisionally turning on the first andsecond emitting devices.
 10. The apparatus according to claim 1, whereinlight sources included in the light emitting portion includes a red LEDwhich emits red light, a green LED which emits green light, and a blueLED which emits blue light.
 11. A method for processing image dataoutputted by an image sensor including a light emitting portion, aphotoelectric conversion portion in which a plurality of photoelectrictransducers are arrayed in line, and a charge transfer portion whichtransfers charges stored in the photoelectric conversion portion,comprising: outputting image data corresponding to a plurality ofpixels; for the image data outputted by the image sensor, obtaining adifference between brightness values of a first color component and asecond color component; for a smear occurred at the charge transferportion, obtaining a reference smear amount data corresponding to eachof color components of light from the light emitting portion and acorrection target pixel; obtaining a correction amount for a brightnessvalue from the difference between the brightness values and thereference smear amount data; and correcting a brightness value of theimage data outputted by the image sensor based on the correction amount.12. An apparatus comprising: a first obtaining unit constructed toobtain image data, corresponding to a plurality of pixels, outputtedfrom an image sensor which includes a light source, a photoelectricconversion portion in which a plurality of photoelectric transducers arearrayed, and a transfer portion which transfers charges stored in thephotoelectric conversion portion; a second obtaining unit which, withrespect to a smear occurred at the transfer portion, is constructed toobtain information on a reference smear amount corresponding to a firstcolor component of light emitted by the light source and correspondingto a correction target pixel; and a correction unit which, based on abrightness value difference between a brightness value of a first colorcomponent of the image data obtained by the first obtaining unit and abrightness value of a second color component of the image data obtainedby the first obtaining unit, and based on the information on thereference smear amount obtained by the second obtaining unit, isconstructed to correct the brightness value of the first color componentof the image data obtained by the first obtaining unit.
 13. Theapparatus according to claim 12, wherein the correction unit is furtherconstructed to obtain a correction amount of the brightness value of thefirst color component of the image data, based on the brightness valuedifference and the information on the reference smear amount, and tocorrect the brightness value of the first color component of the imagedata obtained by the first obtaining unit, based on the correctionamount of the brightness value of the first color component of the imagedata.
 14. The apparatus according to claim 13, wherein the correctionunit is further constructed to obtain a correction amount of thebrightness value of the first color component of the image data, basedon a brightness value difference between a brightness value of the firstcolor component of the image data when the reference smear amount occursand a brightness value of the second color component of the image datawhen the reference smear amount occurs, and based on the information onthe reference smear amount.
 15. The apparatus according to claim 13,wherein the image data obtained by the first obtaining unit is obtainedby emitting the first color component of the light from the lightsource, and then continuously emitting the second color component of thelight from the light source, and wherein the correction amount isobtained from the brightness value of the first color component of theimage data obtained by the first obtaining unit and the brightness valueof the second color component of the image data obtained by the firstobtaining unit at a same pixel position in a direction in which theplurality of photoelectric transducers are arrayed.
 16. The apparatusaccording to claim 12, wherein the image data obtained by the firstobtaining unit is obtained by emitting the first color component of thelight from the light source, and then continuously emitting the secondcolor component of the light from the light source.
 17. The apparatusaccording to claim 12, wherein the reference smear amount is specific toa position of the correction target pixel in a direction in which theplurality of photoelectric transducers are arrayed.
 18. The apparatusaccording to claim 12, wherein the image data obtained by the firstobtaining unit is obtained by line-sequentially reading an imageoriginal while moving the image sensor.
 19. The apparatus according toclaim 12, wherein the light source time-divisionally emits each colorcomponent for each line.
 20. The apparatus according to claim 12,further comprising the image sensor.
 21. The apparatus according toclaim 12, further comprising an image processing unit.
 22. The apparatusaccording to claim 12, further comprising a memory unit for storing theinformation on the reference smear amount.
 23. A method comprising:obtaining image data, corresponding to a plurality of pixels, outputtedfrom an image sensor which includes a light source, a photoelectricconversion portion in which a plurality of photoelectric transducers arearrayed, and a transfer portion which transfers charges stored in thephotoelectric conversion portion; for a smear occurred at the transferportion, obtaining information on a reference smear amount correspondingto a first color component of light emitted by the light source andcorresponding to a correction target pixel; and based on a brightnessvalue difference between a brightness value of a first color componentof the obtained image data and a brightness value of a second colorcomponent of the obtained image data, and based on the obtainedinformation on the reference smear amount, correcting the brightnessvalue of the first color component of the obtained image data.